Porous Reservoirs Formed From Side-By-Side Bicomponent Fibers

ABSTRACT

The invention is generally directed to a fluid transmissive body comprising side-by-side bicomponent fibers bonded to each other at spaced apart contact points to form a self-sustaining, three dimensional bonded fiber structure, wherein each of the side-by-side bicomponent fibers comprise a first fiber component having a first softening temperature and a second fiber component having a second softening temperature, wherein the first softening temperature is greater than the second softening temperature and wherein a cross sectional area of the first fiber component comprises between 40%-85% of a cross-sectional area of the side-by-side bicomponent fiber.

This application claims priority to Provisional Application Ser. No. 60/887,880, filed on Feb. 2, 2007, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention is generally directed to three dimensional, self-sustaining, bonded fiber structures formed from bicomponent fibers in which the polymeric components of the fiber are generally arranged in a side-by-side manner. More specifically, the invention is directed to three dimensional, self-sustaining bonded fiber structures that are particularly adapted to be used as ink reservoirs in various applications.

Multicomponent fibers contain two or more discrete polymeric entities in a single fiber or in arrangements of fibers. A subset of multicomponent fibers is bicomponent fibers. A bicomponent fiber is a multicomponent fiber with only two polymeric entities. Bicomponent fibers may be manufactured in various cross-sections, including but not limited to a side-by-side structure, a centric sheath-core structure, an acentric sheath-core structure, or other architectures such as segmented pies and “islands in the sea.”

Multicomponent fibers are typically manufactured by melt spinning techniques (including conventional melt spinning, melt blowing, spun bond, and other melt spun methods). The fibers can be used in continuous filament or staple form and may be collected into webs or tows. They may be produced alone or as part of a mixed fiber system. Moreover, multicomponent fibers can be used for a variety of purposes, including but not limited to forming woven and non-woven fabrics or structures as well as bonded or non-bonded structures.

As described in U.S. Pat. Nos. 5,607,766, 5,620,641, 5,633,082, 6,103,181, 6,330,883, 6,814,911, 6,840,692, and U.S. patent application Ser. No. 11/333,499, filed Jan. 17, 2006, each of which is incorporated herein by reference in its entirety, there are many forms of and uses for bonded fiber structures, as well as many methods of manufacture. In general, such bonded fiber structures are formed of thermoplastic fibrous material, the bonded fiber structure comprising an interconnecting network of highly dispersed fibers bonded to each other at their points of contact. The resulting structures are substantially self-sustaining, three-dimensional porous components and structures, which may be produced in a variety of sizes and shapes.

The materials used in a particular bonded fiber structure may be tailored to specific applications. For example, specific fiber types or fiber components in the case of a multicomponent fiber, may be selected to provide a particular set of fluid manipulation properties and/or facilitate processing. Some fiber types or fiber components may provide a higher surface energy that would facilitate wicking of certain fluids. Other fiber types or fiber components may provide bonding advantages. In some multicomponent fibers, a plurality of different fiber components may be used to provide a particular combination of characteristics.

Porous, bonded structures formed from multicomponent fibers have demonstrated distinct advantages for fluid storage and fluid manipulation applications, because such bonded fiber structures have been shown to take up liquids of various formulations and release them in a predictable and reproducible manner. A typical use for these structures may include use as nibs for writing instruments, ink reservoirs for use in writing instruments and ink jet printer cartridges, wicks for a wide variety of devices and applications, including point of care lateral flow diagnostic devices and wicks for air fresheners, depth filters, and other applications where the characteristics of such structures are advantageous. Many of the advantageous characteristics of bonded fiber structures stem from the materials used in the multicomponent fibers from which these structures are formed.

Porous Ink Jet Printer (IJP) cartridge ink reservoirs have been made of reticulated polyurethane foam, felt, and self-sustaining, three dimensional structures formed from sheath-core bicomponent fibers. When the IJP cartridge ink reservoir is made from reticulated polyurethane foam, the foam is typically die-cut or stamped from a larger pad or block of foam. The dimensions of the cut or stamped reservoir are generally larger than the cartridge space the reservoir will occupy (oversize fit). During manufacturing of the IJP cartridge, the foam is compressed into the smaller space formed by the inside of the cartridge. IJP cartridge manufacturers utilize this technique to adjust the capillary pressure (and subsequent ink release and anti-leak properties of the reservoir), with higher compression (and less porosity) meaning a higher capillary pressure (lower ink release, greater ink resistance).

Felt IJP cartridge ink reservoirs are also typically cut or stamped from a larger piece of felt.

Ink reservoirs have also been made using sheath-core bicomponent fibers. U.S. Pat. No. 6,394,591 to Higuma, et al., for example, describes ink reservoirs for ink jet printer cartridges containing fibrous materials formed from sheath-core bicomponent fibers. The dimensions of these bonded fiber components are generally larger than the cartridge space the reservoir will occupy, and, as reported in Higuma et al., are compressed to fit into these spaces.

Bonded, self-sustaining, three dimensional, fibrous structure reservoirs have been formed from sheath-core bicomponent fibers produced using melt blowing methods. Such methods and products are described in U.S. Pat. No. 5,607,766 to Berger, U.S. Pat. No. 5,620,641 to Berger, U.S. Pat. No. 5,633,082 to Berger, U.S. patent application No. 10/743,593 to Ward et al., and U.S. patent application Ser. No. 11/333,499 to Ward et al., each of which is incorporated herein by reference in its entirety. Bonded fibrous structure reservoirs described by the above references are typically manufactured to the same or very nearly the same dimensions of the cartridge space the reservoir will occupy. This provides advantages during the manufacture of IJP cartridges in that loading machinery and techniques are less complex, and the loading rate of bonded fiber reservoirs is typically faster when a reservoir compression step is avoided.

Ink reservoirs are ideally fashioned to meet performance requirements for leak resistance and ink extraction. A critical function of an ink reservoir is not only to release the ink for printing through the print head during normal operation of the IJP, but also to contain and hold the ink within the cartridge during various stresses. Stresses are often the most extreme during shipping, when they can include changes in atmospheric pressure, shock or impact from dropping and rough handling, and various thermal cycles. It is known to those skilled in the art that a higher degree of pore size (or capillary) uniformity in the reservoir media will lead to a more consistent back pressure during the extraction of ink from the reservoir. With more uniform pore size, and concomitant uniformity of back pressure, one can design a reservoir that will maximize the amount of ink that may be extracted, while, at the same time, maintaining a higher degree of leakage resistance than would otherwise be observed in a reservoir with a more broad pore size distribution.

Ink extraction is also important because ink used in ink jet printers may be expensive (on the order of $20/kg and greater). Typical reservoirs (such as those made from melt blown fibers or polyurethane foam) allow ink to be extracted only to a level of approximately 60-70%; thus leaving 30-40% of the ink unusable inside the cartridge. It is a large economic incentive to an ink jet manufacturer if a greater percentage of ink can be extracted from a cartridge. A manufacturer could inject significantly less ink into the cartridge while still getting the same page count, thus resulting in considerable savings.

In the case of porous foam, felt, and fiber-based reservoir systems, the capillary pressure characteristics of the reservoir may be designed to meet particular leak resistance requirements. Capillary pressure characteristics may be modified through variation of reservoir material surface energy, pore size, and surface to volume ratio of the reservoir material itself. Even the surface tension and viscosity of the ink may be modified to meet particular leak resistance requirements.

Accordingly, ink jet printer reservoirs that have increased ink retention, ink extraction, and leak resistance are desirable. Moreover, reservoirs that may be formed into complex shapes (as opposed to regular rectangular blocks or cylinders), and may therefore fit into the housings of ink jet cartridges or other ink delivery devices (such as a marker pen or other writing instrument) are also desirable.

SUMMARY OF THE INVENTION

Aspects of the invention include a fluid transmissive body comprising side-by-side bicomponent fibers bonded to each other at spaced apart contact points to form a self-sustaining, three dimensional bonded fiber structure, wherein each of the side-by-side bicomponent fibers comprise a first fiber component having a first softening temperature and a second fiber component having a second softening temperature, wherein the first softening temperature is greater than the second softening temperature and wherein a cross sectional area of the first fiber component comprises between 40%-85% of a cross-sectional area of the side-by-side bicomponent fiber.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings constitute a part of the specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to assist in the understanding of the invention, reference will now be made to the appended drawings, in which like reference characters refer to like elements. The drawings are exemplary only, and should not be construed as limiting the invention.

FIG. 1 is a cross-sectional view of a two-component, three dimensional side-by-side bicomponent fiber structure in accordance with some embodiments of the invention.

FIG. 2 is a cross-sectional view of another two-component, three dimensional side-by-side bicomponent fiber structure in accordance with some embodiments of the invention.

FIG. 3 depicts multiple cross-sectional views of exemplary complex, three dimensional structures which may be formed from side-by-side bicomponent fibers in accordance with some embodiments of the invention.

FIG. 4 is a graph illustrating the extraction results for reservoirs according to some embodiments of the invention.

FIG. 5 is an isometric view of an ink jet cartridge in accordance with some embodiments of the invention.

FIG. 6 is a graph illustrating the compressive force results for side-by-side fibers (“SBS” for purposes of this figure) and sheath core fibers (“S/C” for purposes of this figure) in accordance with some embodiments of the invention.

FIG. 7A is an isometric view of a writing device, in accordance with some embodiments of the invention.

FIG. 7B is an isometric view of a wick/nib combination, made from a bonded fiber structure, in accordance with some embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.

The term “bicomponent fiber” as used herein refers to the use of two polymers of different chemical nature placed in discrete portions of a fiber structure. As used herein, the term “side-by-side bicomponent fiber” refers to a fiber that has a first distinct polymeric component, and a second distinct polymeric component, the first of which has a greater softening point than the other, wherein the cross-sectional area of the first fiber component comprises 40%-85% of the cross-sectional area of the side-by-side bicomponent fiber. In this case, the outer surface of the fiber will have an area comprising the first polymer, and another area comprising the second polymer. As used herein, side-by-side bicomponent fibers may also be referred to as “SBS fibers.”

The term “structure component” as used herein refers to a distinct portion of a multi-component structure that is uniform in material and properties.

Side-By-Side Bicomponent Fibers

Exemplary side-by-side bicomponent fibers are shown in FIGS. 1 and 2. With reference to FIG. 1, an SBS bicomponent fiber 10 in accordance with some embodiments of the invention may take the cross sectional form of “married half moons.” The SBS bicomponent fiber 10 may be comprised of a first fiber component 100 and a second fiber component 110. In some embodiments of the invention, the first fiber component 100 may have a higher melting or softening temperature than the second fiber component 110. For example, in some embodiments of the invention, the second fiber component may have a softening temperature of less than 100° C. Additionally, in some embodiments of the invention, the second fiber component may have a softening temperature of less than 190° C. With reference to FIG. 2, an SBS bicomponent fiber 20 in accordance with some embodiments of the invention may have a cross-section where a first fiber component 200 forms the predominant portion of the overall fiber cross-section, and a second fiber component 210 may occupy a portion of the outer surface of the overall fiber 20. In some embodiments of the invention, fiber component 200 may have a higher melting or softening temperature than fiber component 210.

SBS bicomponent fibers are distinctly different than sheath-core bicomponent fibers in that in a sheath-core bicomponent fiber the core material is not exposed on the surface of the overall fiber. In contrast, an SBS bicomponent fiber may have a substantial portion of both fiber components present in the macroscopic surface of the fiber.

In accordance with some embodiments of the invention, the first fiber component (100, 200) may comprise a semi-crystalline polymer with a softening point greater than the second fiber component (110, 210), which may also comprise an amorphous or semi-crystalline polymer. SBS bicomponent fibers may be made by a variety of methodologies well known to those skilled in the art including, but not limited to, conventional melt fiber spinning, melt blowing and spun bond processes.

In accordance with some embodiments of the invention, SBS bicomponent fibers may be produced from a number of thermoplastic resins including, but not limited to, polyolefins, polyesters (and copolymers thereof), polyurethanes (and copolymers thereof), and polyamides (and copolymers thereof). As noted above, the first fiber component (100, 200) may have a greater softening temperature and may comprise a material consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), nylon 6, nylon 6,6, and other semicrystalline polyamides (and copolymers thereof), semicyrstaline polyesters, including polybutylene terephthalate and polyethylene terephthalate. The second fiber component (110, 210) may have a lower softening temperature, and may be comprised of a material consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), polyamides, including copolymers thereof, copolymers of polyesters, including copolymers of polybutylene terephthalate and polyethylene terephthalate, elastomeric and plastomeric polypropylenes, styrene-butadiene copolymers, polyisoprene, polyisobutylene, polychloroprene, butadiene-acrylonitrile, elastomeric block olefinic copolymers, elastomeric block co-polyether polyamides, elastomeric block copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea), and elastomeric silicones. Care must be taken in selecting the various materials for the first and second fiber components in order to minimize the possibility of the two fiber components separating during fiber spinning and subsequent processing. Examples of fiber component combinations which may provide minimal separation during fiber spinning and subsequent processing include, but are not limited to, copolypropylene/polypropylene, poly-1-butene/polypropylene, ethylene-octene copolymer/polypropylene and isophthalate-modified co-PET/PET.

SBS bicomponent fibers may be produced by a number of different means, including conventional fiber spinning by melt processes, melt blowing, and spun bond techniques. SBS bicomponent fibers may be produced with fiber diameters ranging from 1-200 microns, and in particular may be produced with fiber diameters in the range of 10-50 microns.

Various techniques are known for the production of products from polymeric fibers. The polymeric fibers themselves may be produced by a number of common techniques, oftentimes dictated by the nature of the polymer and/or the desired properties and applications for the resultant fibers. Among such techniques are conventional melt spinning processes, wherein a molten polymer is pumped under pressure to a spinning head and extruded from spinneret orifices into a multiplicity of continuous fibers. Melt spinning techniques are commonly employed to make both mono-component and bi- or multi-component fibers. In addition, some polymers can be dissolved in a suitable solvent (e.g., cellulose acetate in acetone) of typically 25% polymer and 75% solvent. In a wet spinning process, the solution is pumped at room temperature through the spinneret which is submerged in a bath of a liquid non-solvent in which the non-solvent serves to coagulate the polymer to form polymeric fibers. It is also possible to dry spin the fibers into hot air (or other hot gas), rather than a liquid bath, to evaporate the solvent and form a solid fiber strand. These and other common spinning techniques are well known in the art.

Bicomponent and multi-component fibers may be formed by melt blowing. Briefly, melt-blowing involves the use of a high speed, typically high temperature gas stream at the exit of a fiber extrusion die to attenuate or draw out the fibers while they are in their molten state. See, for example, U.S. Pat. Nos. 3,595,245, 3,615,995 and 3,972,759, the subject matters of which are incorporated herein in their entirety by reference, for a comprehensive discussion of the melt blowing processing.

After spinning, the fibers are typically attenuated. Attenuation can occur by drawing the fibers from the spinning device at a speed faster than their extrusion speed, thereby producing fibers which are finer, i.e. smaller in diameter. This attenuation may be accomplished by taking the fibers up on rolls rotating at a speed faster than the rate of extrusion. Attenuation my also be accomplished by drawing the fibers utilizing draw rolls operating at different speeds. Depending on the nature of the polymer, drawing the fibers in this manner may orient the polymer chains, thus improving the physical properties of the fiber.

SBS bicomponent fibers may be either self-crimped due to a differential in shrinkage behavior between the first and second fiber components, or mechanically crimped. In general, SBS bicomponent fibers have a greater degree, or amplitude, of self-crimping than sheath-core bicomponent fibers. A concentric sheath-core bicomponent fiber is generally not prone to self crimping. An acentric sheath-core bicomponent fiber may exhibit self-crimping behavior. Some SBS bicomponent fibers may self-crimp in three dimensions (e.g., an X, Y, and Z direction), resulting in a three dimensional cork-screw or spiral shape. Even in situations where a SBS bicomponent fiber self-crimps in only two dimensions (e.g., an X and Y dimension), the amplitude of the crimp may be greater than the amplitude of an acentric sheath-core bicomponent fiber of a similar diameter and made from similar materials.

Self-Sustaining Three Dimensional Bonded Fiber Structures using SBS Fibers

Integrally formed three dimensional bonded fiber structures may be made by several manufacturing processes. An example of a process that can be used to make the composite structures of the invention is a pneumatic forming process, such as that disclosed in U.S. Pat. Nos. 3,533,416, 3,599,646 3,637,447 and 3,703,429, each of which is incorporated herein by reference in its entirety. The process utilizes tows of fibers (such as cellulose acetate or nylon), which, when treated with a plasticizer, may be impinged in a forming die to form a porous, three dimensional, self sustaining, bonded fiber structure. The process can be modified to produce the composite structures of the invention by using a forming die having a plurality of zones. Using this die, tows with different fiber sizes, cross sections or feed rates can be used to form composite materials with different configurations.

SBS bicomponent fibers may be used to form self-sustaining three dimensional bonded fiber structures. The SBS fibers may undergo processes to form a sustainable web. The SBS fibers used in the forming process may be in the form of bundled individual filaments, tows, roving or lightly bonded non-woven webs or sheets. The non-woven webs or sheets can be made either by melt blowing techniques, consolidated webs from spun bond processes, or via carding, followed by either through air bonding or needle punching, or by air laid or wet laid forming techniques. The SBS fibers may also be in the form of unconsolidated, opened staple fibers.

The SBS bicomponent fibers may then be gathered in one or more layers and processed through a series of forming dies, which are sized to form the ultimate cross sectional shape of a desired bonded fiber structure. The first die (or dies) may be heated to bond the fibers into a porous, self sustaining rod. This rod may be formed with any desired cross-section including the relatively complex cross-sectional shapes 310, 320, 330, 340, 350, 360, 370 shown in FIG. 3. The rod may then be cut in desired lengths to form individual reservoir elements.

In accordance with some embodiments of the invention, a three-dimensional, self sustaining bonded fiber structure may be produced from a blend or mix of SBS bicomponent staple fibers and a monocomponent staple fiber, such as polypropylene. In the case of filament fibers, blending may be accomplished by use of alternating or mixed fiber systems, such as those described in U.S. Pat. No. 6,103,181 to Berger.

Fibrous products often require, or are enhanced by, the incorporation of an additive or a topical treatment in the fibrous web during manufacture. The addition of selected surfactants or other chemical agents in a particular concentration to a fibrous media to be used as an ink reservoir for marking and writing instruments or ink jet printer reservoirs may modify the surface characteristics of the fibers to enhance absorptiveness and/or compatibility with particular ink formulations. Similarly, wicking materials used in various medical applications may be treated with solutions of active ingredients, such as monoclonal antibodies, to interact with materials passed therethrough.

In some instances, an additive can simply be added to the polymer melt prior to extrusion. However, for many applications this approach either is impossible or inefficient. Alternatively, it is possible to topically apply liquid surface treatments or finishes to the fibrous material during manufacture, such as by soaking the fibrous materials in highly diluted solutions of the additive in an attempt to insure that adequate additive material is incorporated throughout the fibrous structure.

These processes generally results in a fibrous structure with isotropic properties. Methods that involve treating only sections of the fibrous structure which may create anisotropic properties do exist, but difficulties arise in manufacturing components with two or more component structures or substructures, each with different characteristics. This difficulty is increased when the two or more component structures or substructures are not symmetric.

SBS bicomponent fibers are generally well-suited for use in fiber structures because they may have greater loft than sheath-core fibers of comparable polymeric composition, comparable fiber diameter, and comparable cross-sectional geometry, allowing them to better fill the gaps and crevices in three-dimensional structures. SBS bicomponent fibers also spring back into their original shape more quickly because of this loft characteristic. This feature is important to structures where compression is common (such as ink jet printer reservoirs) and the structure has a liquid that would fill the gaps were it not for a quickly uncoiling fiber. Since the entire surface of the fiber is not available for bonding, as is the case with conventional sheath-core fibers, the fibers have less of a tendency to fuse into intractable bundles or ribbons (referred to as “nits” or “clumps”) during processing. These nits and clumps can form inhomogeneties in the three dimensional bonded fiber structures, and cause degradation of liquid storage and wicking properties.

Anisotropic Multiple Component Structures using SBS Bicomponent Fibers

When multiple fiber materials are used in manufacturing techniques commonly known in the art, the overall resultant structure is substantially isotropic; that is, its structural characteristics and resulting properties (e.g., density, porosity, surface area, surface energy, etc.) are substantially uniform throughout the structure. However, a bonded fiber structure may be comprised of two or more distinct components, such as those described in U.S. patent application Ser. No. 11/333,499, filed Jan. 17, 2006, which is incorporated herein by reference in its entirety. By varying material, or at times the fiber types and/or characteristics in each component, an anisotropic multi-component structure may be created. The structure components may differ in various characteristics, including but not limited to, material, density, porosity, surface area, surface energy, finish treatments, particulate loading, etc. Such structures may, for example, be used to establish a density gradient within an ink reservoir, thereby enhancing ink removal from selected areas within the reservoir. Fibers (SBS bicomponent fibers and others) used in the forming process may be in the form of bundled individual filaments, tows, roving or lightly bonded non-woven webs or sheets. The non-woven webs or sheets can be made either by melt blowing techniques, consolidated webs from spun bond processes, or via carding, followed by either through air bonding or needle punching, or by air laid forming techniques. The SBS fibers may also be in the form of unconsolidated, opened staple fibers.

SBS bicomponent fibers may be used to form bonded fiber structure components in anisotropic multicomponent bonded fiber structures. Multicomponent structures may be comprised of two or more distinct structure components, where at least one structure component is a three dimensional bonded fiber component. The distinct structure components may possess different characteristics and/or properties. For example, in a typical embodiment, a multicomponent structure may be comprised of a three dimensional bonded fiber structure component and a non-fibrous structure component. The three dimensional bonded fiber structure component may be comprised of an interconnecting network of highly dispersed fibers bonded to each other at spaced points of contact. The non-fibrous structure component may be, but is not limited to, permeable or impervious membranes, solid components (formed of, e.g. plastic, metal, composites), paper, cloth, or any other material.

Multi-component structures made from a plurality of self-sustaining, three dimensional bonded fiber structures may be manufactured using the same SBS bicomponent fiber materials, but in a different form. For example, one structure component may have long, hot air bonded staple fibers, while another structure component may have continuous fibers or short, air-laid staple fibers of the same material. The different structure components may also have differences as simple as porosity differences (for example, a highly porous, low density layer and a low porosity, high density layer). In this case, the layer with the small pores will typically have a higher capillary strength that that with the larger pores.

Integrally formed three dimensional bonded fiber structures may be made by several manufacturing processes. An example of a process that can be used to make the composite structures of the invention is a pneumatic forming process, such as that disclosed in U.S. Pat. Nos. 3,533,416, 3,599,646 3,637,447 and 3,703,429, each of which is incorporated herein by reference in its entirety. The process utilizes tows of fibers (such as cellulose acetate or nylon), which, when treated with a plasticizer, may be impinged in a forming die to form a porous, three dimensional, self sustaining, bonded fiber structure. The process can be modified to produce the composite structures of the invention by using a forming die having a plurality of zones. Using this die, tows with different fiber sizes, cross sections or feed rates can be used to form composite materials with different configurations.

SBS bicomponent fibers may be used to form self-sustaining three dimensional bonded fiber structures. The SBS fibers may undergo processes to form a sustainable web. The SBS fibers used in the forming process may be in the form of bundled individual filaments, tows, roving or lightly bonded non-woven webs or sheets. The non-woven webs or sheets can be made either by melt blowing techniques, consolidated webs from spun bond processes, or via carding, followed by either through air bonding or needle punching, or by air laid forming techniques. The SBS fibers may also be in the form of unconsolidated, opened staple fibers.

Alternatively, multi-component structures made from different fibrous components may be formed using continuous processing methods similar to those used to produce isotropic fibrous structures. In these methods, one or more of the fibrous components may be formed from fiber feed materials comprising a fiber component formed from a bondable polymer that, upon application of heat will soften and, when in contact with another fiber, bond to that fiber at the contact point. In some cases such bonding can be aided by the addition of chemical plasticizers.

A multicomponent structure may be formed of a first thermoplastic bonded fiber structure component and a second thermoplastic bonded fiber structure component. Each bonded fiber structure component may comprise an interconnecting network of highly dispersed fibers bonded to each other at points of contact. The first and second bonded fiber structure components may be integrally formed to form an overall multi-component three dimensional bonded fiber structure. In some embodiments, the first and second structure components may be coextensive elongate components and the resulting composite structure may be an elongate self-sustaining rod. The cross-section of this resultant rod may exhibit a first area established by the first structure component and a second area established by the second structure component.

An interface may exist between the two or more structure components. If the interface is between two or more fibrous structure components, a portion of the fibers from one component may be bonded to fibers of at least one other structure component. The degree of fiber intermingling between structure components may be dependent upon the manufacturing process used to manufacture the overall integrally formed three dimensional multi-component structure. The interface between two or more structure components wherein one of the components is not a fibrous structure component may or may not have any fiber bonding. This type of interface may be held in place by a mechanical connection, interference fit, friction, or by some fiber bonding. FIG. 3, 330 is illustrative of such as structure.

Multi-component structures having multiple fibrous structure components may have many benefits. For example, structures having at least two three-dimensional bonded fiber structure components with different densities and/or porosities can be used to accommodate different fluid flow characteristics and flow speeds. An application could be as a combination of hydrophobic and hydrophilic structure components. Such a structure may be beneficial in an ink cartridge. The hydrophobic structure component could be used to keep ink away from air vents (preventing leakage) and also keep the ink out of unproductive corners of a reservoir, which would reduce the amount of residual ink in the reservoir upon exhaustion.

Some embodiments of the invention may provide a multi-component structure in which one or more structure components is formed from bonded fiber structures and one or more structure components are formed from other materials. The inclusion of non-fibrous structure components in integrally formed multicomponent structures may provide additional benefits. For example, a permeable or impervious membrane may be included to provide particular fluid treatment properties. Similarly, non-fibrous structure components may be included to provide additional structural, mechanical, filtering, or any other properties.

Although multiple structural components having different materials and different properties have been discussed, it is fully contemplated that the difference between structural components may be more subtle, such as variations in porosity or fiber orientation of otherwise similar materials. Alternatively, structural component differences may be limited to distinct levels of porosity. Since porosity affects capillary strength, altering the porosity level of components may serve to draw fluids from one component to another.

Similarly, altering fiber orientation of a bonded fiber structure has been demonstrated to alter fluid flow. Fluid tends to flow along the length of aligned or partially aligned fibers. Accordingly, by altering the direction or degree of alignment of fibers within a bonded fiber component, fluid flow may be manipulated. Fiber orientation may be varied between fiber components or even within a single fiber component. By altering fiber orientation or alignment, directional fluid transfer (i.e., wicking) may be achieved. In addition, fiber orientation may be varied between a first component that has a high degree of alignment (anisotropic) and a second component that has a lower degree of alignment (more isotropic).

SBS bicomponent fibers are generally well-suited for use in both isotropic and anisotropic multiple component structures because they have typically have greater loft than sheath-core fibers comprised of comparable polymeric composition, comparable fiber diameter, and comparable cross-sectional geometry allowing them to better fill the gaps and crevices in three-dimensional structures. This feature is important to anisotropic multiple component structures where compression is common (such as ink jet printer reservoirs) and the structure has a liquid that would fill the gaps were it not for a quickly uncoiling fiber. Since the entire surface of the fiber is not available for bonding, as is the case with conventional sheath-core fibers, the fibers have less of a tendency to fuse into intractable bundles or ribbons (referred to as “nits” or “clumps”) during processing. These nits and clumps can form inhomogeneties in the three dimensional bonded fiber structures, and cause degradation of liquid storage and wicking properties.

Bonded Fiber Structures using SBS Bicomponent Fibers as Ink Reservoirs

An application for three dimensional, porous, self sustaining, bonded fiber structures described above is as a reservoir for ink storage. In particular, these bonded fiber structures find particular utility as reservoirs for ink jet printer (“IJP”) cartridges. It is well known to those skilled in the art that fiber-based bonded fiber reservoirs present several advantages when used as ink reservoir elements in IJP cartridges. In some cases, such bonded fiber reservoirs can be produced to provide generally more uniform porosity and pore size distribution throughout the bulk of the element, in contrast with previous materials such as reticulated polyurethane foam, which typically exhibits a porosity gradient from top to bottom. The advantage of the consistent porosity provided by bonded fiber structures is that part to part variation in ink holding and release properties is minimized.

Moreover, bonded fiber structures for IJP cartridge applications eliminate the necessity for compression of the element during manufacture. Also, bonded fiber reservoirs do not require either a chemical foaming agent or a pyrolytic reticulation process, and thus present a material which is inherently less prone to contain debris than foam, a clear advantage in use of these bonded fiber materials in IJP reservoir applications.

U.S. Pat. No. 6,394,591 to Higuma, et al. teaches an IJP reservoir material consisting of sheath-core bicomponent fibers wherein the sheath component has a lower melting point than the core component. U.S. Pat. No. 5,607,766 to Berger and U.S. Pat. No. 6,460,985 to Olsen, et al., teaches an IJP reservoir material consisting of sheath-core bicomponent fibers where in the sheath component has a higher melting point than the core component.

With reference to FIG. 5, an ink jet printer cartridge 50 in accordance with some embodiments of the invention will now be described. The ink jet printer cartridge 50, may be generally comprised of a housing 510 and a reservoir 520.

Ink jet housing 510 and associated reservoirs may be generally rectangular in shape, typically with 90 degree angles on all sides. The dimensions of the cartridge can typically range from less than 5 millimeters to 100 millimeters per side. A series of design considerations are often employed, which may include designing a cartridge which can hold six (6) or more reservoirs and which will fit into typical ink jet printer designs. Non-rectangular shapes may also be employed, in which case, the reservoir(s) may be shaped accordingly.

The housing 510 may comprise an air vent 511, a fluid outlet 514, and stand-offs or baffles 513. The air vent 511 may generally be disposed on the top surface of the housing 510, and may allow air to vent into the housing 510, thereby allowing the even flow of ink out of the housing 510. A void 512 may exist near the air vent 511, which may be used to contain ink that may flow out of the reservoir 520 due to environmental conditions. Additionally, the air vent 511 may be used, in certain types of ink jet printer cartridges, to fill the ink jet printer cartridge with ink during assembly.

The fluid outlet 514 may be disposed on the bottom of the housing 510. The fluid outlet may contact a printer head or other device which may draw ink from the housing 510. The outlet may contain a wick, which may draw the ink from the reservoir 520 via increased capillary strength. The stand-offs or baffles 513 may be shoulders or other detents integral to the housing, which may hold the reservoir 520 in a particular location.

The reservoir 520 may be comprised of a porous, three dimensional, self-sustaining bonded fiber structure formed from SBS bicomponent fibers. The bonded fiber reservoir 520 may have a certain capillary pressure that keeps ink inside the reservoir until drawn from the reservoir by either a print head pump or a higher capillary pressure wick. Additionally, the ink reservoir 520 may be designed to have enough capillary force to inhibit leakage as a result of mechanical shock or changes in atmospheric pressure.

The bonded fiber ink reservoir 520 may be formed to dimensions suitable for the housing 510. These dimensions may be slightly oversized, in order to ensure a press-fit of the reservoir 520 in the housing 510, but not so large as to require special compression equipment or processing steps during assembly. The network of SBS bicomponent fibers that comprise the reservoir 520 retains and stores various formulations of ink through the SBS fiber's capillarity characteristics.

As shown in FIG. 6, the generally greater loft of an SBS bicomponent fiber is particularly suited for use in three-dimensional, self sustaining bonded fiber structures where compression is possible, such as in an ink jet printer reservoir. FIG. 6 shows a graph that plots the compressive force versus the compressive distance for both SBS bicomponent fibers and sheath core fibers. In this case, both the sheath core fiber and the SBS bicomponent fiber are comprised of similar materials, with a similar fiber diameter, and a similar cross-sectional geometry, with a first part of polypropylene and a second part of a co-polyethylene. The greater loft of the SBS bicomponent fibers creates a better seal or interference fit against the walls of the structure than the sheath core fibers. The better seal created by the SBS bicomponent fibers can better prevent air passages or gaps from forming which can lead to leakage from a structure containing fluid.

Typical reservoir materials (such as melt blown fibers or polyurethane foam) allow ink to be extracted only to a level of approximately 60-70%; thus leaving 30-40% of the ink unusable inside the cartridge. It is a large economic incentive to an ink jet manufacturer if a greater percentage of ink can be extracted from a cartridge. A manufacturer could inject significantly less ink into the cartridge while still getting the same page count, thus resulting in considerable savings. The ink reservoir created using SBS bicomponent fibers typically results in an ink extraction efficiency (the amount of ink extracted from the reservoir divided by the amount of ink originally placed in the reservoir) of more than 70%.

SBS bicomponent fibers are well-suited for use in ink jet reservoirs because they have greater loft than sheath-core fibers, allowing them to better fill the reservoir's gaps and crevices, and spring back into their original shape quickly. This feature is important to lessen the chance for liquid leakage.

Ink Cartridge Testing Procedure

The ink leakage and ink extraction properties of some embodiments of ink reservoirs in accordance with the invention were determined by the testing procedures below. Reservoirs were constructed using the following techniques:

-   -   a. Reservoir I: A reservoir constructed via the technique         described in the first embodiment, where the low melting second         fiber component consisted of a co-polyethylene and the high         melting first fiber component consisted of polypropylene. Fibers         were conventionally melt spun and had a size of 25 microns. The         fiber cross-section was similar to that shown in FIG. 2. The         fibers were coated with a hydrophilic finish at a level of about         0.4% by weight on the fiber. The SBS staple fibers were         converted into a non-woven web using a carding/through air         bonding technique, then formed using heating and cooling dies         and cut to final shape.     -   b. Reservoir II: A reservoir was constructed via the technique         described in the first embodiment, where the low melting second         fiber component consisted of a co-polyethylene and the high         melting first fiber component consisted of polypropylene. Fibers         were conventionally melt spun and had a size of 25 microns. The         fiber cross-section was similar to that shown in FIG. 2. The         fibers were coated with a hydrophilic finish at a level of about         0.4% by weight on the fiber. The SBS staple fibers were         converted into a non-woven web using an air laid/through air         bonding technique, and then formed using heating and cooling         dies and cut to final shape.     -   c. Reservoir III: This reservoir was constructed via techniques         similar to Reservoir I, except that the fiber used was a sheath         core bicomponent fiber of equivalent materials.     -   d. Reservoir IV: A comparative reservoir was constructed using         melt blown sheath-core bicomponent fibers. The sheath component         was polyethylene terephthalate and the core component was         polypropylene. Fibers had an average size of 16 microns. The         fibers were finish free. The melt blown fibers were directly         formed using heating and cooling dies and cut to final shape.

The reservoirs “I” through “IV” were each formed with the approximate dimensions 27 mm×13 mm×56 mm, producing an approximate volume of 20 cm³. A series of densities (ranging from 0.080 to 0.170 g/cc which give a corresponding series of pore volumes ranging from 0.91 to 0.81) was made to evaluate the effect of density and porosity on ink extraction and leak resistance performance. Ink Jet cartridges were assembled with the reservoirs, and 13.0-13.5 grams of a cyan ink with surface tension of 30 dyne/cm were loaded into the cartridge using an automatic ink injector.

Leak Testing Procedures

Leakage testing was also performed on the cartridges containing the reservoirs of various construction and density. The following protocol was used:

-   -   1. Bonded fiber reservoirs were placed in ink jet printer         cartridges, and the reservoirs were loaded with their specified         ink loads. The ink was allowed to equilibrate in the cartridges         for 30 minutes.     -   2. After the ink equilibrated in the cartridges, the cartridges         were then dropped from a height of approximately 1 meter on each         face of the cartridge, for a total of six drops per cartridge.         The cartridges were then checked for leakage. Any loss of ink         from the reservoir and cartridge qualified as a failure.     -   3. If the cartridges passed the leakage drop test, the         cartridges were then subjected to vacuum leak testing. The         cartridges were placed in a vacuum chamber with the cartridge         tops facing downward and tested for leakage in the following         manner:         -   a. The vacuum in the vacuum chamber was increased from 0.0             to 9.5 in Hg over 1 minute. This vacuum pressure reading was             held for 2 minutes.         -   b. The vacuum in the vacuum chamber was then increase from             9.5 to 12.5 in Hg over 1 minute. This vacuum pressure             reading was held for 2 minutes.     -   4. The cartridges were then removed from the vacuum chamber and         checked for any evidence of leakage. Any loss of ink from the         reservoir and cartridge qualified as a failure.

Cartridges were deemed to have passed the leak test if three replicates showed no evidence of leakage after testing. If one or more cartridges leaked, then the cartridges with reservoirs at a certain density were deemed to have failed the test.

Cartridges that passed the leak test procedure were then tested for ink extraction, as detailed below. Cartridges that failed the leak test were not tested for extraction and the data were not plotted.

Ink Extraction Testing Procedures

The ink was then extracted from cartridge using the following extraction protocol:

-   -   1. The reservoirs were placed in ink jet printer cartridges, and         the specified amount of ink was loaded into the reservoirs.         Thirty (30) minutes were allowed for the ink to equilibrate in         the cartridges.     -   2. After the ink equilibrated in the cartridges, the initial         mass of the cartridge was recorded.     -   3. The cartridges were then placed in an ink extraction         instrument, and ink was extracted as follows for color         cartridges:         -   a. Ink was extracted at a rate of 2.00 mL/minute until a             total of 4.00 mL was extracted.         -   b. Ink was extracted at a rate of 1.00 mL/minute until a             total of 5.00 mL was extracted.         -   c. Ink was extracted at a rate of 0.50 mL/minute until a             total of 5.50 mL was extracted.         -   d. Ink was extracted at a rate of 0.25 mL/minute until 8 in.             H₂O of backpressure was reached.

Extraction results were plotted, showing the extraction percentage (ink extracted divided by ink loaded) for each reservoir as a function of porosity. Porosity was determined by subtracting from a theoretically fully porous structure, which is deemed to be one, the quotient of the density of the reservoir divided by the specific gravity of the aggregate of the polymers in the fiber matrix. Extraction results were plotted only for reservoirs which passed the leakage test. Results are shown in FIG. 4.

From these results, it was determined that the reservoirs “I” and “II” constructed from SBS fibers were equivalent in ink extraction performance to sheath core fibers “III” and had had significantly higher extraction performance than the melt blown sheath-core fiber-based reservoirs “IV.”

Bonded SBS Fiber Structures in Writing Instruments

The side-by-side bicomponent fiber structures of the invention may also be used in a writing instrument. With reference to FIGS. 7A and 7B, a writing instrument 1200 may comprise one or more three dimensional bonded SBS fiber structures disposed within an instrument body. FIG. 7B illustrates a bonded fiber structure 1210 having a wick or reservoir portion 1211 and a nib portion 1212 in accordance with a particular embodiment of the invention. Either or both the wick or reservoir portion 1211 and the nib portion 1212 may be formed from SBS fibers according to the methods described above. The wick or reservoir 1211 and the nib 1212 may be integrally formed in a single bonded fiber structure. The nib may be further processed, for example chiseled into its final shape suitable for use in a writing instrument. Alternatively, a separate nib piece may be mechanically inserted into the formed reservoir and nib combination.

It will be apparent to those skilled in the art that various modifications and variations can be made in the method, manufacture, configuration, and/or use of the present invention without departing from the scope or spirit of the invention. 

1. A fluid transmissive body comprising side-by-side bicomponent fibers bonded to each other at spaced apart contact points to form a self-sustaining, three dimensional bonded fiber structure, wherein each of the side-by-side bicomponent fibers comprise: a first fiber component having a first softening temperature; and a second fiber component having a second softening temperature; wherein the first softening temperature is greater than the second softening temperature; and wherein a cross sectional area of the first fiber component comprises between 40%-85% of a cross-sectional area of the side-by-side bicomponent fiber.
 2. The fluid transmissive body of claim 1, wherein the first fiber component comprises a material selected from the group consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), nylon 6, nylon 6,6, and other semicrystalline polyamides (and copolymers thereof), semicyrstaline polyesters, including polybutylene terephthalate and polyethylene terephthalate.
 3. The fluid transmissive body of claim 1, wherein the second fiber component comprises a material selected from the group consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), polyamides, including copolymers thereof, copolymers of polyesters, including copolymers of polybutylene terephthalate and polyethylene terephthalate, elastomeric and plastomeric polypropylenes, styrene-butadiene copolymers, polyisoprene, polyisobutylene, polychloroprene, butadiene-acrylonitrile, elastomeric block olefinic copolymers, elastomeric block co-polyether polyamides, elastomeric block copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea), and elastomeric silicones.
 4. The fluid transmissive body of claim 1, wherein the first fiber component is a polypropylene material, and the second fiber component is a polyethylene copolymer material.
 5. The fluid transmissive body of claim 1, wherein the side-by-side bicomponent fibers are produced from a number of thermoplastic resins consisting of polyolefins, polyesters, polyurethanes, and polyamides.
 6. The fluid transmissive body of claim 1, wherein the second softening temperature is less than 100° C.
 7. The fluid transmissive body of claim 1, wherein the second softening temperature is less than 190° C.
 8. The fluid transmissive body of claim 1, wherein the self-sustaining, three dimensional bonded fiber structure, is produced from a plurality of fibers, at least some of which are side-by-side bicomponent fibers.
 9. The fluid transmissive body of claim 1, wherein the side-by-side bicomponent fibers have a diameter in a range from about 1 micron to about 200 microns.
 10. The fluid transmissive body of claim 1, wherein the side-by-side bicomponent fibers have a diameter in a range from about 10 microns to about 50 microns.
 11. The fluid transmissive body of claim 1, wherein the side-by-side bicomponent fibers comprise materials that are selected, at least in part, for their compatibility with a particular ink formulation.
 12. The fluid transmissive body of claim 1, further comprising a plurality of structure components wherein each structure component has an interface with at least one other structure component, and wherein at least one of the plurality of structure components is the self-sustaining, three dimensional bonded fiber structure.
 13. The fluid transmissive body of claim 12, comprising at least a first structure component and a second structure component, wherein the first structure component has an interface with the second structure component, the first structure component has a first set of fiber characteristics, the second structure component has a second set of fiber characteristics, and the first and second sets of fiber characteristics are selected so as to establish a surface energy gradient across the interface between the first and second structure components.
 14. An ink jet printer cartridge, comprising: a housing defining a reservoir cavity; and a reservoir disposed within the reservoir cavity, the reservoir comprising a plurality of side-by-side bicomponent fibers, bonded to each other at spaced apart contact points to form a self-sustaining, three dimensional bonded fiber structure, wherein the plurality of side-by-side bicomponent fibers comprise: a first fiber component having a first softening temperature; and a second fiber component having a second softening temperature; wherein the first softening temperature is greater than the second softening temperature, wherein a cross sectional area of the first fiber component comprises between 40%-85% of a cross-sectional area of the side-by-side bicomponent fiber.
 15. The ink jet printer cartridge of claim 14, wherein the first fiber component of the side-by-side bicomponent fiber comprises a material selected from the group consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), nylon 6, nylon 6,6, and other semicrystalline polyamides (and copolymers thereof), semicyrstaline polyesters, including polybutylene terephthalate and polyethylene terephthalate.
 16. The ink jet printer cartridge of claim 14, wherein the second fiber component of the side-by-side bicomponent fiber comprises a material selected from the group consisting of polyethylene (and copolymers thereof), polypropylene (and copolymers thereof), polyamides, including copolymers thereof, copolymers of polyesters, including copolymers of polybutylene terephthalate and polyethylene terephthalate, elastomeric and plastomeric polypropylenes, styrene-butadiene copolymers, polyisoprene, polyisobutylene, polychloroprene, butadiene-acrylonitrile, elastomeric block olefinic copolymers, elastomeric block co-polyether polyamides, elastomeric block copolyesters, poly(ether-urethane-urea), poly(ester-urethane-urea), and elastomeric silicones.
 17. The ink jet printer cartridge of claim 14, wherein the second softening is less than 100° C.
 18. The ink jet printer cartridge of claim 14, wherein the second softening temperature is less than 190° C.
 19. The ink jet printer cartridge of claim 14, wherein the first fiber component is a polypropylene material, and the second fiber component is a polyethylene copolymer material.
 20. The ink jet printer cartridge of claim 14, wherein the side-by-side bicomponent fibers are produced from a number of thermoplastic resins consisting of polyolefins, polyesters, polyurethanes, and polyamides.
 21. The ink jet printer cartridge of claim 14, wherein the reservoir is produced from a blend of side-by-side bicomponent fibers.
 22. The ink jet printer cartridge of claim 14, wherein the side-by-side bicomponent fibers have a diameter in a range from about 1 micron to about 200 microns.
 23. The ink jet printer cartridge of claim 14, wherein the side-by-side bicomponent fibers have a diameter in a range from about 10 microns to about 50 microns.
 24. The ink jet printer cartridge of claim 14, wherein the side-by-side bicomponent fibers comprise materials that are selected, at least in part, for their compatibility with a particular ink formulation.
 25. The ink jet printer cartridge of claim 14, wherein the side-by-side bicomponent fibers are configured to provide a reservoir with an ink extraction efficiency of at least 70%.
 26. The ink jet printer cartridge of claim 14, wherein the bonded fiber structure is adapted to take up, hold, and controllably release a particular ink formulation.
 27. A writing instrument comprising: a housing defining a reservoir cavity; and a self-sustaining, three dimensional bonded fiber structure disposed within the reservoir cavity, the self-sustaining, three dimensional bonded fiber structure comprising a plurality of side-by-side bicomponent fibers, bonded to each other at spaced apart contact points, each of the plurality of side-by-side bicomponent fibers comprising a first fiber component having a first softening temperature and a second fiber component having a second softening temperature, the first softening temperature being greater than the second softening temperature, wherein a cross sectional area of the first fiber component comprises between 40%-85% of a cross-sectional area of the side-by-side bicomponent fiber, and wherein the self-sustaining, three dimensional bonded fiber structure is one of the set consisting of an ink reservoir, a wick, and a nib. 